Cyanide - compound found in almonds. When boiled down they get released. Ingestion of cyanide blocks a pathway of the electron transport chain (the oxygen acceptor stage). So if you decide to taste it for yourself, you will have a matter of seconds before you die :).
Its not cyanide, its arsenic. Cyanide kills you in a matter of seconds, and just seconds after taking it, your body goes into convulsions...... Nobody has ever been told the taste of cyanide, but its said to be tasteless and odourless.